Low toxicity polyurethane composition
produced from long chain aliphatic
ddsocyanates

ABSTRACT

POLYURETHANE COMPOSITIONS PREPARED BY THE REACTION OF A HYDROXYL CONTAINING POLYESTER FREE OF REACTIVE UNSATURATION AND AN ALIPHATIC DIISOCYANATE HAVING THE FORMULA   O=C=N-CH2-(CH2)Y-CH(-(CH2)X-CH3)-(CH2)Z-N=C=O   WHEREIN Z IS 0 TO 2, X AND Y ARE INTEGERS FROM 0 TO 19 AND THE SUM OF X AND Y IS FROM 7 TO 19. THE POLYURETHANES PRODUCED PROVIDE HARD, FLEXIBLE, NON-TOXIC COATINGS AND CASTINGS.

. Re. 27,054 Reissued Feb. 9, .1971

27 054 LOW TOXICITY POLYUltETHANE COMPOSITION PRODUCED FROM LONG CHAIN ALlPHATlC DHSOCYANATES Anthony J.. Castro, Oak Park, and Layton F. Kinney,

- Chicago, Ill., assignors to Armourjlndustrial Chemical Company, Chicago, III., a corporation of Delaware No Drawing. Original No. 3,487,050, dated Dec. 30, 1969, Ser. No'. 706,777, Feb. 20, 1968. Application for reissue Jan. 26, 1970, Ser. No. 10,669

Int. Cl. C08g 17/003, 22/18, 51/36 US. Cl. 260-75 8 Claims Matter enclosed in heavy brackets ['1 appears in the original patent but forms no part of this reissue specification; matter made by reissue.

ABSTRACT OF THE DISCLOSURE Polyurethane compositions prepared by the reaction ofa hydroxyl containing polyester free of reactive unsaturation' and an aliphatic diisocyanate having the formula BACKGROUND OF THE INVENTION Resinous polyurethane materials have heretofore been provided by reacting diisocyanates, such as toluene diisocyanate, with non-reactive polyurethanes containing available hydroxyl groups. The properties of the resulting polyurethane resins depend to a large extent upon the Organic compounds used as reactants. Polyurethanes obtained by using aromatic diisocyanates, such as toluene diisocyanate, are highly susceptible tosunlight degradation producing a yellowing of the polyurethane. Such discoloration renders coatings of such polyurethanes unsatisfactory when clear coatings are desired. Use of aliphatic diisocyanate, on the other hand, produces polyurethanes resisting degradation, but until this invention only polyurethanes from lower aliphatic diisocyanates, such as hexamethylene diisocyanate, have beenproduced. Hexamethylene diisocyanate produced polyurethane is not satisfactory due to the' extremely high toxicity ofhexamethylene diisocyanate. The residual diisocyanate present in the polyurethane renders the product commercially unacceptable due primarily to toxicity. Prior attempts to use other aliphatic diisocyanates, such as diisocyanate from dimer acid derived diamines, have not proved satisfactory to form coatings or castings, due to the extremely soft and rubbery nature of the cured polyurethane.

SUMMARY OF THE INVENTION It is, therefore, an object of this invention to provide a relatively non-toxic polyurethane composition, cured polyurethane coatings and castings therefrom which are hard but relatively flexible, and a process for preparation of such polyurethane composition. It is another object of this invention to provide polyurethane resins which not only have excellent physical properties for coatings and castings, but also have improved resistance to degradation from ultra-violet radiation.

This invention provides a polyurethane resin by reactprinted in italics indicates the additionsing. non-reactive polyester" and diisocyanate having r the;

formula wherein z is aninteger'fr'omUto 2, x'andy are integers" from 0 to 19 and the sum of X and y. is from- 7 "to-19" The polyurethaneformedin this'manner is especially, satisfactory forthe production of coatings and castings which are' hard, .flexible, resistant to sunlight degrada' tion, and are non=toxic, even when they contain residual diisocyanates.

The polyester ingredient formed byesterification of polybasic' acid and polyhydrie alcohol preferably hasa relatively high hydroxyl value, lowacid value, an'd "is soluble andliquid or fusible. The -acid ingredient of-the polyester is preferably dibasicandfifree of'reactive un saturation such as olefinic-and acetylenic bonds. The acid may contain non-reactive unsaturation sucli" as is present in the ringstructure of acid, such as-plithalic, terephthalic, isophthalic, and the like. Another suitable group of dicarboxylic acids includes acids in which-the car-boxyl groups" are interconnected by: hydrocarbon groups. Suitable acids-include succinic, adipic, sehacic, azelaic acids, and others containing upto' about 10 carbon atoms. The-acid'anhydrides maybe used as initial ingredients, and mixtures oftwo or more acids and/or anhydrides may be utilized; It is especially preferred to use succinic or adipic acid and/or anhydride. The polyhydric alcohol component of the polyesters may be dihydric, trihydric or higher. Dihydn'c alcohols including propylene glycol, dipropylene glycol, ethylene glycol, diethylene glycol and polyethylene'glycol are suitable. Polyhydric alcohols containing at least three hydr'ic functions suitable to form the polyesters for use in this invention include glycerol, pentaerythritol, trimethylol ethane, trimethylolpropane, mannitol, and the like. Poly esters containing only dihydric alcohols as the alcohol component tend to be more flexible and" thermoplastic than those containing trihydric or higher alcohols which form hard, thermoset resins. Mixtures of the two types of alcohols control the cross-linking in the polyurethane product. The ratio of dihydric to higher polyhydric alcohol may vary widely depending upon properties desired in the resulting polyurethane.

The polyester may be formed according to conventional well known methodsof esterification by heating the mixture of acid and polyhydric alcohol to a temperature sutficiently high to effect evolution of water. The reaction is preferably continued at up to about 250 to 450 F. until the acid value is reduced to below 20, and preferably below about 12. Products of acid values of, below 1 are obtainable. The ratios of hydroxyl functions to carboxyl functions are correspondingly high, forexample, from about 50 up to 500 to 600. The water of reaction is usually stripped from the polyester to provide a' substantially anhydrous product. Usually the residual water will not exceed from about 0.1 to 0.5%.

Diisocyanates suitable for use in our invention have the formula wherein z is an integer from 0 to 2, x and y are integers from 0 to about 19 and the sum of x and y is from about 7 to 19.

Typical compounds which fall within the above formula are diisocyanates derived from diamino compounds including aminolaurylamine, aminomyristylamine, aminopalmitylamine, aminostearylamine, aminoarachidylamine, aminobehenylamine, aminolignocerylamine, aminomethyllaurylamine, aminomethylmyristylamine, aminomethylarachidylamine, aminomethylbenzylamine, aminomethyllignocerylamine, aminoethyllaurylamine, aminoethylmyristylamine, aminoethylpalmitylamine, aminoethylstearylamine, aminoethylarachidylamine, aminoethylbehenylamine, aminoethyllignocerylamine, 9-aminoundecylamine, 9-aminomethy1undecylamine, 9-aminoethylundecylamine, and the like.

Especially preferred diisocyanates are derived from 9(10) aminostearylamine, 9(10) aminomethylstearylamine, 9-aminoundecylamine and 9-aminomethylnndecylamine. Mixtures of two or more diisocyanates may be used.

Suitable diisocyanates may be prepared by reacting a carbonyl halide, such as phosgene with an amino-secondary-alkyl amine. For example, by reacting phosgene with the hydrochloride salt of 961-)-aminomethylstearylamine, at about 50 to 70 for 6 to 7 hours, more than 90 percent overall yield of aminomethylstearylamine diisocyanate may be obtained.

To obtain fully cured polyurethane (interpolymers of the polyester and diisocyanate) coatings and castings in a short period of time, it is preferred to incorporate into either the polyester component, or into the diisocyanate component, or into the mixture of polyester and diisocyanate, a suitable catalyst to promote the reaction. Suitable catalysts include N-methyl morpholine, tertiary amines such as trimethyl amine and triethyl amine, metal salts of organic acids such as zinc octanoate and dibutyl tin dilaurate, and diazabicyclo-alkene compounds selected from the group consisting of 1,5-diazabicyclo-[4.3.0]- nonene-; alkyl-substituted 1,5 diazabicyclo-[4.3.0]-nonene 5; alkoxy-substituted 1,5 diazabicyclo [4.3.0]- nonene-S; 1,5-diazabicyclo-[4.4.01-decene-5; alkyl-substituted 1,5-diazabicyclo-[4.4.0]-decene-5; and alkoxysubstituted 1,5-diazabicyclo-[4.4.0]-decene-5. The diazabicyclo-alkene compounds may be prepared by methods described in Berichte, 99, p. 2012 (1966) or by the cyclization of aliphatic nitriles and pyrrolidone. The diazabicycloalkene compounds suitable for use as catalysts in the invention have the formulas CH3 CHzCHr Cfiz CHl n l in E and g N N N N l i I i z C 2 a 1 wherein R and R are selected from the group consisting of alkyl and alkoxy groups containing from 1-4 carbon atoms. The method of producing polyurethanes using the diazabicyclo-alkene compounds is described in copending US. patent application Ser. No. 654,078, filed July 18, 1967.

The catalyst may be used in an amount from 0 to 10 .weight percent, based upon the diisocyanate. Preferred invention by forming a mixture of the above described polyester and diisocyanate with blending until thoroughly mixed. It is preferred to use approximately stoichiometric amounts of polyester and diisocyanate. The stoichiometric proportions depend upon the nurnber of hydroxy functions per carboxyl function of polyester. Suitable coatings and castings may be prepared using up to 10 percent excess of either the diisocyanate or polyester. In this regard, it is noted that one important advantage of the composition of this invention is that residual diisocyanate may be tolerated in that the aliphatic diiso cyanate called for by this invention is relatively non-toxic. Thus, the polyurethanes formed may be substantially isocyanate 0r hydroxy terminated. In time, terminal isocyanate groups may convert to amines in the presence of moisture followed by reaction of the amine function with residual isocyanate.

Polyurethanes so formed may be used directly as a casting material, producing hard, flexible, non-toxic castings, the hardness of which may be controlled by choice of polyester.

For coating applications, it is frequently desirable to add a solvent to provide polyurethane of the most suitable viscosity. From about 10 to 50 weight percent, based upon the polyurethane composition, organic solvents which do not react with isocyanates, are suitable. Especially suitable are aromatic compounds such as toluene, xylene, Cellosolve acetate, and ketones such as methylisobutyl ketone. Additionally, flow control agents may be added when desired to coating compositions. An especially suitable fiow control agent is a percent silicone resin having a viscosity at 20 C. of 5-30 centipoises 60% in xylol (SR-82, General Electric Company).

Coatings may be formed by casting films on the surface to be coated using the above described polyurethane composition, preferably with a solvent and flow control agent. An especially preferred coating may be prepared by using a polyester having an acid value of about 10 and formed from phthalic anhydride, adipic acid and glycerol in the ratio of from 1:5 :8 respectively. The polyester is blended with a stoichiometric amount of aminostearyl amine diisocyanate and blended until mixed. About 1 Weight percent, based upon the diisocyanate, 1,5-diazabicycle-[4.3.0]-nonene-5, and about 25 weight percent, based upon the total polyurethane composition, of xylene is added with mixing. The resulting composition is cast into a film on tin plate and is cured by heating to about F. for about 15 minutes. A hard, flexible, clear, nontoxic coating is formed.

A surprising and commercially important property of the polyurethane coatings produced by the compositions of this invention is their very low, toxicity. The toxicity of polyurethane compositions results from toxicity of the diisocyanate component. The diisocyanates called for by this invention exhibit very low toxicity. Hexamethylene diisocyanate, using Sprague Dawley rats has been found to have a single oral dose LD of 1.05 grams/kilogram. The recommended permissible vapor concentration of hexamethylene diisocyanate is 0.02 p.p.m. in air. Tests conducted using diisocyanates derived from amino-ethylstearylamine showed the LD of the single oral dose to Sprague Dawley rats to be 21.8 grams/kilogram. Rats subjected to inhalation of diisocyanates derived from aminomethylstearylamine for a 7 /2. hour exposure at a vapor concentration essentially saturated showed no signs of toxicity. Further, when introduced into rabbit eyes diisocyanates derived from animomethylstearylamine was found to be non-irritating. When applied in 0.5 ml. quantities to intact and abraded skin of the rabbits, diisocyanates derived from aminomethylstearylamine produced only a minimal degree of transient irritation. The diisocyanates derived from aminomethylstearylamine would, therefore, appear to present no hazard to health under ordinary conditions of industrial use.

The following examples are presented to illustrate the present invention.

EXAMPLE I A polyester pro-polymer was prepared from 20 grams of. succinic anhydride and 40 grams of trimethylol propane cooked to an acid value of 6 and hydroxyl value of about 478. 4.15 grams of the above described polyester were mixed with 7.5 grams of aminomethylstearylamine diisocyanate, 0.5 gram of zinc octoate, and 10.75 grams of xylene were added with mixing. Using this composition, a film was cast on tin plate and allowed to cure at room temperature. The film was tack-free overnight and exhibited a Sward hardness of 52 after 3 days. The film was clear, hard and flexible.

EXAMPLE II Following the procedure of Example I, 8.3 grams of polyester, as prepared in Example I, were mixed with 5.0 grams aminomethylstearylamine diisocyanate and 6.7 grams of xylene, and 0.5 gram of zinc octoate were added with mixing. A film was cast in the same manner as described in Example I and cured at room temperature. A very satisfactory film resulted. The film exhibited a Sward hardness of 60 after 3 days.

EXAMPLE III A polyurethane composition suitable for castings was prepared by mixing 4.25 grams of polyester, as prepared in Example I, with 8 grams of aminomethylstearylarnine diisocyanate and 0.5 gram of zinc octoate and blended until uniform. The composition was poured into a mold, and a hard, flexible casting was produced upon curing at room temperature.

EXAMPLE IV A polyester pre-polymer is prepared using phthalic and adipic acid and glycerol with mole ratio of 1:5 :8 respectively and cooked to an acid value of about 10. 4.2 grams of this polyester are mixed with 7.5 grams of aminomethylstearylamine diisocyanate, 11 grams of 50 percent xylene and 50 percent methylisobutyl ketone and 0.5 gram of zinc octoate. The composition is cast into a film on tin plate and cured by heating to about 130 C. for about 15 minutes. The film produced is clear, hard and flexible.

While in the foregoing specification this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.

We claim:

1. Polyurethane prepared by a process comprising reacting hydroxyl containing polyester free of reactive unsaturation with diisocyanate having the formula H OHs(CH J(GHi)yCHiN=O=O wherein z is an integer from 0 to 2, x is an integer from 0 to 8, y is an integer from [8] 7 to 19, provided that the sum of x and y is from [8] 7 to 19.

2. The polyurethane of claim 1 wherein said diisocyanate is selected from those derived from diamino compounds of the group consisting of 9(10)-aminostearylamine, 9(10)-aminomethylstearylamine, 9-aminoundecylamine and 9-aminomethylundecylamine.

3. The polyurethane of claim 1 wherein said polyester has an acid value below 20.

4. The polyurethane of claim 1 wherein said polyester has an acid value below 12 and is produced by the esterification of a dibasic carboxylic acid and polyol selected from the group consisting of dihydric and trihydric alcohols.

5. The polyurethane of claim 4 wherein said carboxylic acid is selected from the group consisting of phthalic, terephthalic, isophthalic, succinic and adipic acids and said polyol is selected from the group consisting of propylene glycol, ethylene glycol, glycerol, pentaerythritol and trimethylolpropane.

6. Cured polyurethane prepared by the process [comprising curing polyurethane prepared 'by a process comprising] of reacting hydroxyl containing polyester free from reactive unsaturation with diisocyanate having the formula wherein z is an integer from 0 to 2, x is an integer from 0 to 8, y is an integer from [8] 7 to 19, provided that the sum of x and y is from [8] 7 to 19.

7. Cured polyurethane of claim 6 wherein said [curing is achieved] polyurethane is prepared by heating to about to C. for from about 5 to 20 minutes.

8. Cured polyurethane of claim 6 wherein said [curing is achieved] polyurethane is prepared in the presence of from about 0.5 to 2 weight percent of diazabicyclo-alkene catalyst selected from the group consisting of 1,5-diazabicyclo-(4-.3.0)-nonene-5; alkyl-substituted 1,5-diazabicyclo-(4.3.0)-nonene-5; 1,5-diazabicyclo-(4.4.0)-decene- 5; alkyl substituted 1,5 diazabicyclo-(4.4.0)-decene-5; and alkoxy-substituted 1,5-diazabicyclo-(4.4.0)-decene-5.

References Cited The following references, cited by the Examiner, are of record in the patented file of this patent or the original patent.

UNITED STATES PATENTS 2,650,212 8/1953 Windemuth. 2,753,319 8/ 1956 Brockway. 2,993,047 8/ 1961 Bortnick et al. 3,084,177 4/ 1963 Hostettler et al. 3,356,650 12/1967 McElroy.

HOSEA -E. TAYLOR, Primary Examiner H. S. COCKERAN, Assistant Examiner US. Cl. X.R. 

